The present invention relates to a therapeutic agent for Parkinson's disease containing a xanthine derivative or a salt thereof as an active ingredient. ##STR4##
It is known that adenosine antagonistic action is found in compounds represented by Formula (A) in which R.sup.1c and R.sup.2c represent propyl, R.sup.3c represents hydrogen, and R.sup.4c represents substituted or unsubstituted phenyl, aromatic heterocyclic group, cycloalkyl, styryl, or phenylethyl [J. Med. Chem., 34, 1431 (1991)]. Further, Japanese Published Unexamined Patent Application No. 26516/72 discloses, as brain stimulants, compounds represented by Formula (B) in which R.sup.1d and R.sup.2d independently represent methyl or ethyl, R.sup.3d represents methyl, Y.sup.1d and Y.sup.2d represent hydrogen, and Z.sup.d represents phenyl or 3,4,5-trimethoxyphenyl. WO92/06976 discloses, as adenosine A.sub.2 receptor antagonists, compounds represented by Formula (B) in which R.sup.1d and R.sup.2d independently represent hydrogen, propyl, butyl, or allyl, R.sup.3d represents hydrogen or lower alkyl, Y.sup.1d and Y.sup.2d independently represent hydrogen or methyl, and Z.sup.d represents phenyl, pyridyl, imidazolyl, furyl, or thienyl unsubstituted or substituted by 1 to 3 substituents such as lower alkyl, hydroxy, lower alkoxy, halogen, amino, and nitro. Furthermore, other compounds represented by Formula (B) are known. One is 8-styryl caffeine which is a compound of Formula (B) in which R.sup.1d, R.sup.2d, and R.sup.3d represent methyl, Y.sup.1d and Y.sup.2d represent hydrogen, and Z.sup.d represents phenyl [Chem. Ber. 119, 1525 (1986)]. Another is a compound of Formula (B) in which R.sup.1d, R.sup.2d, and R.sup.3d represent methyl, Y.sup.1d and Y.sup.2d represent hydrogen, and Z.sup.d represents pyridyl, quinolyl, or methoxy-substituted or unsubstituted benzothiazolyl [Chem. Abst. 60, 1741h (1964)]. However, there is no description with regard to the pharmacologic action of any of these compounds.